Tractable Combinations of Global Constraints

We study the complexity of constraint satisfaction problems involving global constraints, i.e., special-purpose constraints provided by a solver and represented implicitly by a parametrised algorithm. Such constraints are widely used; indeed, they are one of the key reasons for the success of constraint programming in solving real-world problems. Previous work has focused on the development of efficient propagators for individual constraints. In this paper, we identify a new tractable class of constraint problems involving global constraints of unbounded arity. To do so, we combine structural restrictions with the observation that some important types of global constraint do not distinguish between large classes of equivalent solutions.Comment: To appear in proceedings of CP'13, LNCS 8124. arXiv admin note: text overlap with arXiv:1307.179

Conserved motifs reveal details of ancestry and structure in the small tim chaperones of the mitochondrial intermembrane space

The mitochondrial inner and outer membranes are composed of a variety of integral membrane proteins, assembled into the membranes posttranslationally. The small translocase of the inner mitochondrial membranes (TIMs) are a group of ∼10 kDa proteins that function as chaperones to ferry the imported proteins across the mitochondrial intermembrane space to the outer and inner membranes. In yeast, there are 5 small TIM proteins: Tim8, Tim9, Tim10, Tim12, and Tim13, with equivalent proteins reported in humans. Using hidden Markov models, we find that many eukaryotes have proteins equivalent to the Tim8 and Tim13 and the Tim9 and Tim10 subunits. Some eukaryotes provide "snapshots" of evolution, with a single protein showing the features of both Tim8 and Tim13, suggesting that a single progenitor gene has given rise to each of the small TIMs through duplication and modification. We show that no "Tim12" family of proteins exist, but rather that variant forms of the cognate small TIMs have been recently duplicated and modified to provide new functions: the yeast Tim12 is a modified form of Tim10, whereas in humans and some protists variant forms of Tim9, Tim8, and Tim13 are found instead. Sequence motif analysis reveals acidic residues conserved in the Tim10 substrate-binding tentacles, whereas more hydrophobic residues are found in the equivalent substrate-binding region of Tim13. The substrate-binding region of Tim10 and Tim13 represent structurally independent domains: when the acidic domain from Tim10 is attached to Tim13, the Tim8–Tim13¹⁰ complex becomes essential and the Tim9–Tim10 complex becomes dispensable. The conserved features in the Tim10 and Tim13 subunits provide distinct binding surfaces to accommodate the broad range of substrate proteins delivered to the mitochondrial inner and outer membranes

Ocular Blood Flow Measurements in Healthy White Subjects Using Laser Speckle Flowgraphy

Purpose. To assess the feasibility and reliability of Laser Speckle Flowgraphy (LSFG) to measure ocular perfusion in a sample of healthy white subjects and to elucidate the age-dependence of the parameters obtained. Methods: This cross-sectional study included 80 eyes of 80 healthy, non-smoking white subjects of Western European descent between 19 and 79 years of age. A commercial LSFG instrument was applied to measure ocular blood flow at the optic nerve head (ONH) three successive times before and after pharmacological pupil dilation. The mean blur rate (MBR), a measure of relative blood flow velocity, was obtained for different regions of the ONH. Eight parameters of ocular perfusion derived from the pulse-waveform analysis of MBR including blowout time (BOT) and falling rate (FR) were also recorded. Results Artifact-free LSFG images meeting the quality criteria for automated image analysis were obtainable in 93.8% without pupil dilation and in 98.8% with pharmacological pupil dilation. Measurements of MBR showed excellent repeatability with intraclass correlation coefficients >= 0.937 and were barely affected by pupil dilation. The majority of pulse-waveform derived variables exhibited equally high repeatability. MBR-related blood flow indices exhibited significant age dependence (p<0.001). FR (r = 0.747, p<0.001) and BOT (r = -0.714, p<0.001) most strongly correlated with age. Conclusions: LSFG represents a reliable method for the quantitative assessment of ocular blood flow in white subjects. Our data affirms that the LSFG-derived variables FR and BOT may be useful biomarkers for age-related changes in ocular perfusion

Optimization Methods for the Partner Units Problem

Abstract. In this work we present the Partner Units Problem as a novel challenge for optimization methods. It captures a certain type of configuration problem that frequently occurs in industry. Unfortunately, it can be shown that in the most general case an optimization version of the problem is intractable. We present and evaluate encodings of the problem in the frameworks of answer set programming, propositional satisfiability testing, constraint solving, and integer programming. We also show how to adapt these encodings to a class of problem instances that we have recently shown to be tractable.

Wettbewerb und Regulierung jetzt auch in der Wasserwirtschaft

Die Verfügungen der Landeskartellbehörde Hessen gegen Wasserversorger wegen zu hoher Wasserpreise, die auf eine Vergleichsmarktanalyse gestützt wurden, und deren Bestätigung durch den BGH am 2.2.2010 waren erste Vorboten einer sich verschärfenden kartellrechtlichen Entgeltkontrolle der Wasserwirtschaft. Die folgende Entscheidung der Landeskartellbehörde Baden-Württemberg auf der Basis einer Kostenanalyse ein Jahr später ist dagegen unlängst vom OLG Stuttgart gestoppt worden. Vor dem Hintergrund der dadurch ausgelösten Unsicherheiten stellt sich die Frage, ob die Wasserwirtschaft nicht wie die anderen Netzwirtschaften (Telekommunikation, Energie, Post, Eisenbahntransport) auch einer Regulierung durch die in den übrigen Wirtschaftszweigen erfolgreich tätige Bundesnetzagentur unterworfen werden sollte. Der Beitrag gelangt zu dem Ergebnis, dass der kartellrechtliche Ansatz gegenwärtig sinnvoll ist und die Option auf eine abgabenrechtliche Kontrolle beseitigt werden muss. Sollte sich die kartellrechtliche Kontrolle jedoch nicht als wirksam herausstellen, so wäre eine bundeseinheitliche, sektorspezifische Lösung zu prüfen. Summary In the past, the Hessian Cartel Authority issued orders against water suppliers because they were charging excessively high prices and abused their dominant position. Those decisions were based on an analysis of comparable markets. These orders were upheld by the Federal Surpreme Court (BGH) on February 2, 2010. In this development one can see somewhat of a forerunner of a pricing regulation through antitrust law within the water industry. However, the following decision by the Cartel Authority of Baden-Wuerttemberg one year later, which was based on an analysis of the actual costs was only recently quashed by the Higher Regional Court (OLG) of Stuttgart. Considering the resulting insecurities regarding the application of the legal framework, the question arises, whether the water suppliers should be subjected to regulation by the Federal Network Authority – just like other network based industries, such as telecommunications, energy, post and railways. This paper comes to the conclusion that the current approach using the antitrust law is generally reasonable as a first step. What seems even more important than the choice between a sector specific regulation and antitrust law is to abolish the option of an administrative price control of public water suppliers which proved to be ineffective. Should the full application of cartel law, however, turn out to be ineffective in the future, a national sector specific solution should be considered. JEL Classification: K

Scientific Reports / Retinal oxygen extraction in humans

Adequate function of the retina is dependent on proper oxygen supply. In humans, the inner retina is oxygenated via the retinal circulation. We present a method to calculate total retinal oxygen extraction based on measurement of total retinal blood flow using dual-beam bidirectional Doppler optical coherence tomography and measurement of oxygen saturation by spectrophotometry. These measurements were done on 8 healthy subjects while breathing ambient room air and 100% oxygen. Total retinal blood flow was 44.39.0l/min during baseline and decreased to 18.74.2l/min during 100% oxygen breathing (P<0.001) resulting in a pronounced decrease in retinal oxygen extraction from 2.330.51l(O2)/min to 0.880.14l(O2)/min during breathing of 100% oxygen. The method presented in this paper may have significant potential to study oxygen metabolism in hypoxic retinal diseases such as diabetic retinopathy.(VLID)491093